1. Field of the Invention
The present invention relates to a mold attaching/detaching apparatus and a method for attaching/detaching metal molds to and from the stationary platen and movable plate of a molding machine such as a resin molding machine or a die casting machine.
2. Description of the Related Art
A fixing apparatus is disclosed in, for example, JP 2005-246634A1, which is used as an apparatus for respectively fixing a metal mold to the stationary platen and movable plate of a resin molding machine, for example. This fixing apparatus has two electromagnet devices that are provided on the stationary platen and the movable plate of the resin molding machine, respectively. When supplied with a current, the electromagnet devices generate magnetic fields, which magnetically attract and secure the metal molds to the resin molding machine.
The fixing apparatus can easily attach and detach the metal molds, merely by supplying an electric current to the electromagnet devices and stopping the current supply to the electromagnet devices, irrespective of the position where the metal molds are secured to the stationary platen and the movable plate. This can enhance the efficiency of attaching and detaching the metal molds.
Various metal molds different in size must be attached to the resin molding machine, in accordance with the types of moldings to be formed. If the metal molds to be attached are small, the area at which they contact the stationary platen and movable plate is small, and the magnetic attractive force is reduced. Inevitably, the small metal molds cannot be firmly secured to the resin molding machine.
In the case where small metal molds are so secured to the resin molding machine by the electromagnetic devices, they may partially easily move from the stationary platen and the movable plate, respectively, due to the force applied to them as the molding is pulled from them. When the metal molds partially so move from the stationary platen and movable plate, the magnetic force acting on the metal molds fast decreases, possibly causing the molds to fall from the stationary platen and movable plate. Consequently, the molding cannot proceed safely, and the molding efficiency is impaired.
In order to keep the two metal molds to be secured to the stationary platen and movable plate, an electric current must be continuously supplied to both electromagnet devices. This results in an increase in power consumption, ultimately increasing the running cost of the fixing apparatus.
Further, in order to keep both metal molds secured to a holding plate to attain security of operation even at the power failure, a mechanical fixing apparatus or a vacuum suction apparatus must be used in addition to the electromagnetic devices. However, if such a fixing apparatus is arranged with respect to the stationary platen and the movable plate, it requires a large installation space. A sufficient installation space is available if the resin molding machine has a large stationary platen and a large movable plate, but such space can hardly be available if the resin molding machine is small.
Assume that a vacuum suction apparatus is used and secured to the holding plate. Then, not only a sufficient installation space must be provided as pointed out above, but also the vacuum suction apparatus must be continuously driven in order to keep holding the molds. Air consumption inevitably increases, and maintenance cost increase accordingly.
The metal molds may be fixed to the stationary platen and the movable plate with bolts. In this case, the operator must keep pushing the metal molds onto the stationary platen and the movable plate, until the bolts are tightened, firmly fixing the molds to the stationary platen and the movable plate with the bolts. To detach the metal molds from the stationary platen and the movable plate, the operator must move the molds from the stationary platen and the movable plate, while loosening the bolts. Thus, much time and labor are required to attach and detach the metal molds to and from the stationary platen and the movable plate.